The six groups cover all ages and include: Heavy drinking men, young healthy women, wealthy and healthy pensioners, poorly but happy pensioners, people who are unhappy and anxious in middle-age and the long-term sick.

Sheffield university scientists who carried out the study argue that identifying these sub-groups and treating individuals who have a Body Mass Index (BMI) of 30 or above according to their “type” could be a more effective use of NHS services.

Policies designed to tackle obesity and encourage healthier lifestyles often target individuals just because they are obese

Dr Mark Green, researcher

Researcher Dr Mark Green said: “Policies designed to tackle obesity and encourage healthier lifestyles often target individuals just because they are obese.

"But a focus on just the group as a whole is not very efficient. We are all different and different health promotion approaches work for different people.”

The study comes as experts say decades of a “one size fits all” diets and exercises have failed to beat the bulge and left the NHS struggling.

Body mass, measuring a person’s weight in relation to height, is the traditional way of telling if someone is normal, overweight or obese.

But specialists argue the method is outdated and fails to take into account stress and a complex web of emotional issues.

Those with a normal weight have a BMI between 18.5 and 24.9, overweight people are between 25 and 29.9 and the obese have a score of 30 or higher.

But the latest study of almost 30,000 people – of whom more than 4,000 were obese – took into account age, sex, ethnicity and socio-economic ­deprivation and how satisfied they were with their lives.

They were also asked whether they smoked, the number of units of ­alcohol consumed weekly, how often they were active and their efforts to eat healthily.

The researchers found unhappy and anxious middle-aged people were mainly women with poor mental health, reporting high levels of insomnia, anxiety, depression and fatigue.

Those deemed physically sick but happy showed a higher prevalence of chronic conditions such as osteo­arthritis, diabetes and high blood pressure, but low levels of anxiety and depression.

The affluent healthy and elderly group included a large proportion with high blood pressure who drank above average amounts of alcohol.

Their findings are published in the respected Journal of Public Health.